Cut apart cube with text
If I got what you mean, it's not easy, but it can be done, imho. 

But you have to be willing to do some retopology, because you need text mesh (blender always creates this from font object with bad topology) and booleans, two times (produces bad topology)... 

first, experiment with a little cube base and a single letter, trust me.


create the box base and text mesh and ensure it has good topology (all quads, no doubles, a good mesh)





boolean "union" of the box and the text.




with more complex setups, it is a good idea to retolopogize the applied union result (all quads, no doubles, a good mesh) - optional but suggested


create the jigsaw pieces, as a single object but separated islands, ie: the pieces.  (again, ensure all quads, no doubles, a good mesh), and scale this mesh to make its bounds to "surround" the previous base+text union.  




seeing this in transparency:




boolean "intersection" of the base+text with the "surrounding" jigsaw mesh (see settings on the right)




which gives you